In wide band communication, such as according to the UMTS (Universal Telecommunications Systems) standard using the telecommunication technology WCDMA (Wideband Call Division Multiple Access), the transmitter and the receiver of a portable radio communication apparatus are active simultaneously. Also, it is often required that a portable radio communication apparatus, such as a mobile telephone, in addition to an internal or external mounted antenna comprises an external antenna connector, to which an auxiliary antenna can be connected. The auxiliary antenna may be embodied as an external car antenna, which is adapted to provide an antenna signal, which is common for all operating frequencies of the mobile telephone. As a consequence of these requirements, the front end RF architecture of the communication apparatus, which is common to the receiver and transmitter circuits gets quite complicated with many components introducing signal losses between the antenna and the receiver. The RF architecture requires e.g. transmit and receive signals to be fed to a filter, such as a diplex filter, in order to combine the signals to a common antenna outlet and/or a common external antenna outlet, such as the external antenna connector, of the communication apparatus. Conventionally, the receiver and the transmitter of the communication apparatus are connected to the antenna through the filter, which facilitates the simultaneous two-way communication.
A further requirement in telecommunication technology is to facilitate dual or multi-mode communication functionality. Therefore, the communication apparatus comprises additional receiver and transmitter circuits for communicating over frequency bands other the frequency band of the WCDMA mode, such as the 900 MHz GSM (Global System for Mobile communication) and the 1800 DCS (Digital Cellular System). If dual or multi-mode communication is provided, additional antenna mode circuits/switches and filters have to be provided. However, the circuits/switches between the WCDMA receiver and the antenna of the mobile terminal will still introduce the unfavorable amount of insertion losses degrading the WCDMA receiver performance. In a typical mobile terminal having an internal antenna combined with an external antenna connector provided in the signal path between the WCDMA receiver and the auxiliary antenna connected via an antenna connector and coaxial cable, the RF-loss budget can be:
Diplex filter3.0 dBMulti-mode antenna switch0.5 dBCombining filter0.5 dBExternal antenna connector0.2 dBCoaxial cable and connector0.8 dBSum5.0 dB
The components between the receiver circuits and the antenna introduce obviously substantial losses when the communication apparatus is utilized in the WCDMA mode. Also, if a common external antenna connector is provided, the antenna signal should be common for all frequency bands of operation. As can be seen above, in particular the diplex filter provided for the simultaneous two-way communication of the WCDMA mode introduces substantial losses.
In the communication technology, it is known to provide separate transmit and receive antennas in a communication apparatus. However, if it is preferred to also provide an external antenna connector in such an apparatus a selection problem will arise. If the receiver is connected to both the receive antenna and an auxiliary antenna via the external antenna connector a selection problem will be introduced. Somehow selection between the signal from the receive antenna or the auxiliary antenna has to be provided.